1. Field of the Invention
This invention relates to an optical measurement arrangement which includes a detector array assembly having a plurality of detector elements. More specifically, the invention relates to an optical measurement arrangement which corrects the power changes occurring in the optical measurement arrangement when performing the optical measurement of a signal which is a result of a light illumination. The optical measurement arrangement of the invention may find particular application in an optical analyzer for analyzing urine samples.
2. Description of Related Art
In general, current-day practice for identifying micro-organisms, e.g., bacteria in urine specimens involves a complex, lengthy and expensive process for identifying and specifying micro-organisms in microbiology labs. In the current process, the specimens are accepted into the lab. These specimens are then sorted and labeled and then they are inoculated onto blood agar medium using sterilized loop. The specimens are then inserted into a dedicated incubator for a 24-hour period. A day later, the lab technicians screen the specimens for positive and negative cultures. In general, most of the cultures are negative and they are manually reported. The organisms for the positive cultures are isolated and suspended in a biochemical fluid. This involves suspension, dilution, vortexing and turbidity measurements resulting in biochemical waste products. The cultures are then subjected to a species identification and antibiotics susceptibility testing exposing the suspensions to multiple reagents. After another 6- to 24-hour incubation period, the findings are interpreted and reported by lab technicians. This entire process generally takes 11 steps and 50 hours to obtain specimen results and the process is labor intensive.
WIPO Publication No. WO 2009/049171 filed Oct. 10, 2008 and entitled “SYSTEM FOR CONDUCTING THE IDENTIFICATION OF BACTERIA IN URINE” discloses a system for identifying bacteria in urine samples and includes: 1) a disposable cartridge or holder for holding disposable components including a centrifuge tube, two pipette tips with a different volume capacity and an optical cup or cuvette; 2) a sample processor for processing or preparing the urine samples; and 3) an optical analyzer for analyzing the processed urine samples. The disposable cartridge with its four components is used in the sample processor and the optical cup or cuvette, in particular, is used in the optical analyzer.
In this system of the aforementioned WIPO Publication No. WO 2009/049171 the urine samples are contained within disposable cartridges which hold disposable components, i.e., a centrifuge, two pipette tips with a different volume and an optical cuvette. The cartridges are bar coded and tied in with the patient's ID. The cartridges are inserted in a magazine which is then inserted into a sample processor which processes the specimens. The prepared specimens are injected into the optical cuvettes which are then inserted into an optical analyzer which analyzes the specimens. The optical analyzer analyses and generates the complete results enabling ultimate treatment of the bacteria. The system does not require a sophisticated operator and gives rapid results. The system increases efficiency, improves workload, saves time and money and is easy to operate. The sample preparation can be performed in parallel with the specimen analysis process and from 1 to 50 specimens can be analyzed simultaneously.
This system of WIPO Publication No. WO 2009/049171 includes a plurality of disposable cartridges for holding a plurality of disposable components including a centrifuge tube, a first pipette tip with a 1 ml volume; an optical urine sample cuvette, and a second pipette tip with a 0.5 ml volume; a sample processor for receiving the plurality of disposable cartridges and configured to process and prepare the urine sample of each disposable cartridge and to transfer the urine samples into the respective optical cuvette of each of the disposable cartridges; and an optical analyzer for receiving the optical cuvettes containing the processed urine samples and analyzing and generating the specimen results. The entire procedure for processing the urine specimens in the sample processor and analyzing them in the optical analyzer takes about 20 minutes for a single specimen and up to 2 hours for 50 specimens.
A related method for identifying the type of micro-organism in a urine sample includes the steps of obtaining a urine sample; passing the urine sample through an eleven micron filter; obtaining a 2 ml sample of the filtered urine and placing it into a centrifuge tube; obtaining a 1,000,000:1 dilution of the dissolved materials in the urine retaining bacteria in the urine sample by centrifuging the 2 ml sample at about a 12,000 g-force, decanting about 95% of the fluid in the centrifuge tube, replacing the decanted solution with a saline solution and repeating these steps about five times; transferring the final solution into an optical cup; subjecting the optical cup to an optical analysis having optics which include exciting the urine sample with different wavelengths, collecting and detecting the fluorescent emissions; and directing the fluorescent emissions into a spectrometer which may be part of an optical analyzer of the system of WIPO Publication No. WO 2009/049171.
The optical analyzer used in the aforementioned WIPO Publication No. WO 2009/049171 may include an optical measurement arrangement for optically analyzing the bacteria in urine samples. Currently, when performing an optical measurement of a signal, which is a result of a light source, e.g., a UV light source, the signal will change with a change in the intensity of the light illumination; however, this change does not reflect a change in the measurement variable, e.g. the bacteria in the sample. Previous attempts for correcting the power changes to signals represented by the intensity of the light in an optical measurement arrangement involved splitting the illumination beam into at least a first split beam and a second split beam and then measuring the changes in the second split beam by using a detector assembly, such as a photodiode or PMT (photomultiplier tube). Although the intensity of the second split beam, which is measured by the detector assembly, may represent a change in the first split beam, this intensity of the second split beam will also be affected by any changes occurring in the detector assembly due to factors such as aging, temperature and spectral and/or intensity responses in the detector assembly. Thus, a correction to the intensity of the signal represented by the first split illumination beam based on the intensity of the second split beam being detected by the detector assembly of the prior art optical measurement arrangements, will introduce errors into the power correction to the intensity signal of the illumination beam of these optical measurement arrangements.
Examples of optical measurement arrangements are disclosed in U.S. Pat. Nos. 6,515,745; 6,559,941; 6,773,922; 7,206,620; 7,299,079; and 7,303,922.
There is a need in the art to enhance the power correction to a light source of an optical measurement arrangement by providing a correction signal to the illumination beam that is free from errors existing in the detector assembly used to measure the intensity of the illumination beam generated by the light source.